The present invention relates to coating dies. More particularly, the present invention relates to coating strips of flowable material on a substrate.
A variety of techniques are known for forming multiple strips of a composition onto a substrate. In those processes, a composition is applied to a web in the form a plurality of strips, each of which is separated from an adjacent strip by a region which is uncovered. One example of an extrusion type apparatus used in this type of process is described in U.S. Pat. No. 4,106,437, incorporated by reference herein. Extrusion type dies are disadvantaged in that as the composition is extruded onto the substrate, the composition can xe2x80x9cneck downxe2x80x9d or decrease in width and thickness between the exit of the die and the substrate. In certain applications, this method cannot generate sufficiently precise strip widths and thicknesses.
An alternate process for applying strips to substrate is contact coating type dies. In contact coating, the die is disposed close to the substrate so that xe2x80x9cnecking downxe2x80x9d of the composition is eliminated. Thickness of the composition is adjusted by pulling the composition through a clearance between the substrate and an obstruction. When the end process involves dispensing relatively viscous material (e.g., greater than 1000 centipoise) the coating die can be subjected to high pressures which act to deform the structure of the die. A common required characteristic of the strips is a uniform cross-sectional profile. Deflection of the die can result in a non-uniform cross-sectional profile of the flowable material being coated onto the substrate. An additional requirement in certain applications is to maintain the edges of the strip of flowable material to a high level of precision (e.g., perpendicular to the substrate). Additionally, in some contact dies, as the substrate moves relative to the die, it is common for the substrate to wear on a portion of the die so that this portion would eventually require replacement. The rubbing of the substrate on the die can also cause a xe2x80x9cnecking downxe2x80x9d of the web, potentially causing variation in strip width. This xe2x80x9cnecking downxe2x80x9d can also affect the variety of substrates which can be used with the die.
Achieving a precise profile of the strip of flowable material along with precise edge definition as well as decreasing the amount of wear on the die are desirable improvements in strip coating technology. In particular, the uncoated portion of the substrate typically is the portion of the substrate which wears on the die. Thus, as the uncoated portion of the substrate increased, the wear of the substrate on the die increased, having the effect of limiting the percentage of uncoated substrate which can be manufactured due to the high wear of the die.
The invention is a contact die for dispensing of flowable material on a substrate. The contact die includes at least one die block including a first internal passage. A die lip portion is disposed on the die block having a lateral dimension. A first plurality of orifices is disposed through the die lip portion proximate to each other and in communication with the internal passage to dispense flowable material as a single strip on the substrate. A first edge is disposed on one lateral side of the first plurality of orifices to direct-the flowable material.
The die is used to dispose flowable material onto the substrate by translating the flowable material through the first internal passage in the die block. The flowable material is translated through the first array of orifices through the die lip and in communication with the first internal passage. The die lip has a lateral dimension. The flowable material is directed with the first edge. The first edge is proximate one lateral side of the first array of orifices. One edge of the first strip of flowable material on the substrate is defined with the first edge.